“I don’t consider myself a runner. I don’t really enjoy it that much,” said 25-year-old Braintree native David St. Germain.

On Monday, Patriot’s Day, it’s not a stretch to say, that of the thousands of runners who will gather in Hopkinton for the start of the 117th running of the Boston Marathon, that sentiment puts St. Germain in a unique category.

The primary goal and motivation for the pediatric nurse employed by Mass. General Hospital is raising money for cancer research for the Dana-Farber Marathon Challenge Team.

And despite his non-runner manifesto, this will be the Boston College grad’s (Class of 2009) fourth run.

St. Germain’s journey to Boston began 22 years ago when cancer struck his family. His 3-month-old brother Alex was diagnosed with a rare cancerous tumor of the retina, which ultimately cost him his right eye. But the skill of the doctors at the Dana-Farber Cancer Institute saved the sight in the other.

“I obviously don’t remember, I was still a toddler, but my mother always tells me, especially around marathon time, that I used to refer to Alex’s tumors as boo-boos,” St. Germain said. “And there is no doubt that my brother is my inspiration to work with people in the medical area, as well as motivating me to run”.

The former biology major knew that he would never to be able to meet his age group’s 3:05 qualifying time, but securing a spot on the Dana-Farber’s race team solved that dilemma.

“For the 2008 race, I applied to run for their Marathon Challenge Team. It was just something I felt driven to do because of the cause – raising money for Dana-Farber and its cancer research,” St. Germain said.

“I received a phone call telling me that I was part of the team and that’s when a certain reality hit home. I said, ‘Wow! I really need to start running.’ I’m actually going to do this.”

Self-admittedly in terrible shape, the BC alum’s first attempts were slow. But through perseverance, proper coaching, and most importantly, the spirit of his brother Alex, St. Germain evolved into a full-fledged member of the running community.

“It was my junior year at BC and I started training by running around the reservoir, which is located just down from the campus at Cleveland Circle. But I was so out of shape, after about a mile, I had to stop, I was totally out of breath. I thought, ‘How the heck am I going to run 26.2 miles?’ But every time I went out, I just pushed a little bit further,” he said.

He passed the toughest physical test in his four years at the Heights on the day he was driven out and dropped off in Hopkinton, with his legs and feet the only mode of transportation back to campus.

Page 2 of 2 - “My best friend dropped me off in Hopkinton and said, ‘I’ll see you back at BC.’ I had no alternative but to keep running and that was my first long run. When I hit 21 miles, I found myself right in front of my dorm gate, and that’s when I knew, I can actually do this.”

The novice, inspired by the energy and support of the Boston crowd, turned in a respectable time of 3:56 in his initial foray.

This year St. Germain, who is battling tendinitis in his ankle and his knee, has spent more time on a training bike and elliptical machine than running on the road.

“I am nervous this year. I do have concerns about finishing,” he said.

But if anything can pull him through, it’s his Dana-Farber crusade and the notion of his brother waiting by the finish.

“Dana-Farber is the reason that motivates me to do the training to run the marathon,” said the man who doesn’t like to run.

“My family always stands on the same little rise on Boylston Street a couple of hundred yards from the finish line. When I come by I always give Alex a big sweaty hug and he breaks into a huge smile.”

It was St. Germain’s mother Gail who best captured the spirit of her son’s running.

“Dana-Farber has been a great place for support for our family for many years. Its motto, ‘Dedicated to Discovery; Committed to Care,’ well, those are words we all should live by,” she said.